The present invention relates to sorting device for flat mail items featuring at least one input station, one mail item singulation unit in each case and a subsequent transport device for transporting the singulated mail items past process devices such as readers, barcode printers to a loading station of an mail item buffer receptacle, with the buffer receptacle consisting of a number of storage pockets circulating in a conveyor past the loading stations which are loaded with the mail items in the loading stations.
For sorting flat mail items, such as letters, postcards, circulars and such like in accordance with the distribution information specified on their surface the known method is to put these items into special pocket-shaped containers, transport them and output them in a controlled way.
Thus a sorting device is known from EP 0 608 161 A1 in which flat objects are transported sideways by means of channel-shaped, fixed-position feeding device from outside into storage pockets. These storage pockets circulating in a closed loop are moved horizontally past the feeding device and, when flaps are explicitly opened in accordance with the sort specifications, they fall into sorting containers located below the flaps. To feed the items securely into the moving sorting pockets the items must either be moving very quickly in the feed devices, which can result in damage when the items are decelerated in the containers, or the speed of the storage pockets is very slow or the containers come to a halt while the items are fed into them, which means that the throughput of the machine is reduced.
To arrange the items in a specific order a solution is known (EP 820 818 A1) which uses an intermediate receptacle consisting of storage pockets circulating in a conveyor with a least two semicircular conveyor sections on a conveyor device, each of which accepts a mail item and can output this item on command into the actual stacker. In this case all items to be arranged are initially accommodated in any sequence in storage pockets of the intermediate receptacle. Then the items are taken from the storage pockets of the intermediate receptacle and transferred into the stackers such that in the latter they are in the intended order. The stackers which are open at the top are located along the straight sections of the conveyor below the storage pockets.
To improve the feeding of the items into the storage pockets, the end section of the means of transport is embodied in accordance with WO 97/10904 so that it can swivel, so that when the relevant item is being fed in this end section is swiveled at essentially the same speed and in the same direction as the moving storage pocket and is swiveled back at the end of the feeding-in process.
The throughput of this sort device is limited by the throughput of the circulating storage pockets. An increase in throughput can theoretically only be achieved by increasing the speed and/or reducing the spacing of the transport system of the storage pockets. As described however (moving the items into the storage pockets) this is only possible to a very limited extent.
Also known is a sorting device (EP 0 949 015 A2) with a number of input units, at least one mail item buffer with continuously circulating storage pockets, mail item containers as sorting end points which are filled from the lowest mail item buffer receptacle and with a feeder and removal device for mail item containers. In this case it is possible to make do with fewer sorting end points than there are sorting destinations.
Furthermore a sorting device is known from U.S. Pat. No. 6,126,017 A with a continuously circulating mail item buffer receptacle, fixed intermediate receptacles arranged below this and fixed, but exchangeable mail item containers arranged below these.